1. Field of the Invention
The invention relates to a debarking shaft for a debarking machine, and more particularly to an arrangement for fixing teeth to the debarking shaft for debarking logs.
2. Description of the Related Art
Debarking machines are used to strip the bark from logs prior to use of the logs for making paper or other wood products. Debarking machines typically employ a number of rotatable debarking shafts extending parallel to logs to be fed therethrough. The shafts are provided with a number of teeth extending beyond the circumferential surface of the shaft and adapted to strip bark off the logs transversely to the lengthwise direction of the logs and at the same to convey the logs transversely relative to said shafts. Damaged and/or worn teeth must be replaced to maintain the effectiveness of the debarking machine. Debarking machines are described in U.S. Pat. Nos. 4,685,498 and 5,394,912.
In these and other typical debarking machines, the teeth are generally mounted fixedly in certain positions. In one application, the individual teeth are replaceable, but even in that case the position of a tooth on the shaft remains always the same. Further, the individual replacement of worn teeth necessitates taking the debarking machine out of service for an extended time.
According to the invention, these and other deficiencies of the prior art are overcome by means of a debarking shaft in which the debarking shaft teeth are designed as a number of annular tooth rims, each of said tooth rims comprising two or more releasably connected elements. The outer periphery of the tooth rims are provided with the teeth and the inner periphery of said elements are configured to fit around a body of the debarking shaft by way of press clamping.
The tooth rim elements are preferably provided with clamping means for forcing the elements toward each other against the body member of a debarking shaft. The clamping means may comprise for example a headless screw, having one end provided with a left-handed thread and the other end with a right-handed thread, as well as a gripping section between the threads for turning the headless screw.
The debarking shaft is preferably in the form of a circular pipe. Thus, adjacent tooth rims present on a common shaft can be readily locked or clamped on the shaft at an angular position arbitrarily different from each other in the shaft rotating direction, the teeth of adjacent tooth rims being capable of providing the shaft e.g. with helixes. The relative axial distance in between tooth rims can also be adjusted as desired. The debarking shaft has its body member provided, preferably for each tooth rim, with a guide element, preferably a key and slot, for guiding the tooth rims into position.
The body member of the debarking shaft may also be configured in its cross-section as a polygon, whereby the tooth rims can be readily guided and clamped to various angular positions.
The teeth are preferably designed to be effective in both rotating directions of debarking shafts. The teeth effective in opposite rotating directions can be different from or similar to each other. When using different types of teeth in opposite rotating directions, the various rotating directions shall result in different barking capacities, e.g. for wintertime barking and summertime barking. It is also possible to use sharp teeth for the debarking of initially hard-to-bark or frozen logs, while worn teeth can be used for the treatment of easy-to-bark logs. The replacement is effected simply by dismounting a tooth rim and by remounting the same after turning it around.
Making one or more sections of a tooth rim toothless can also influence barking capacity. Hence, some of the tooth rims on a debarking shaft can be completely or partially toothless.
An object of the invention to provide a debarking shaft for a debarking machine, wherein the teeth of a toothed debarking shaft are readily removable and replaceable, as well as reversible regarding the rotating direction thereof.
Another object of the invention is to enable an axial and peripheral displacement and locking or clamping of teeth to a desired position.